The celebrity comet 3I/ATLAS is showing itself out of our solar system for good — but not before the cosmic paparazzi at Earth’s space agencies snap some of the clearest photos of it yet.
Discovered in late June and confirmed to be the third known interstellar object in July, 3I/ATLAS has spent the past several months zooming through the inner solar system at an estimated 130,000 mph (210,000 km/h). The massive, jet-spewing snowball made its closest approaches to Mars and the sun in October. It is due for its closest encounter with Earth on Dec. 19, when it will be about 170 million miles (270 million kilometers) away — nearly twice the distance between our planet and the sun.
Hubble doubles down
On Thursday (Dec. 4), NASA shared the latest image of 3I/ATLAS taken by the Hubble Space Telescope. The glowing white dot at the center of the image shows the comet’s nucleus (its main body) and coma, the bright atmosphere of gas and dust that wraps around the comet before getting funneled into its tail. In the background, stars are stretched into long streaks as Hubble’s camera stays fixed on the fast-moving comet.
Comets typically brighten as they approach the sun, when the ice within them heats up and sublimates. Solar radiation pushes this gas into a tail that stretches away from the sun. Meanwhile, the warmest, sun-facing side of the comet may erupt with jets of gas and dust angled toward our star. Both of these features are faintly visible in the new Hubble image.
NASA snapped this image on Nov. 30, when Hubble was about 178 million miles (286 million km) from the comet. This is considerably closer than when Hubble first imaged the comet in late July. Although that first view showed little more than a blue blur, it nevertheless allowed scientists to constrain 3I/ATLAS’ size to somewhere between 1,400 feet (440 meters) and 3.5 miles (5.6 km) wide — likely the largest interstellar object seen to date.
New data from this image, including details of the coma’s composition, has yet to be released but is likely on the way.
ESA juices up
Also on Thursday, ESA shared its latest view of the comet, taken by the Jupiter Icy Moons Explorer (Juice) orbiter on its way to study Jupiter’s moons for signs of life. Juice snapped the image Nov. 2, just days after 3I/ATLAS’ close approach to the sun.
Located even closer to its target than Hubble (only 41 million miles, or 66 million km, away), Juice shows us a comet brimming with activity.
“Not only do we clearly see the glowing halo of gas surrounding the comet known as its coma, we also see a hint of two tails,” an ESA spokesperson wrote in a statement. “The comet’s ‘plasma tail’ — made up of electrically charged gas, stretches out towards the top of the frame. We may also be able to see a fainter ‘dust tail’ — made up of tiny solid particles — stretching to the lower left of the frame.”
Earth gets ready
Juice observed 3I/ATLAS with five scientific instruments on two days. But besides this teaser image, we don’t yet know what those instruments saw; the full data set won’t reach Earth until late February 2026, according to ESA. That’s because Juice is currently using its main antenna as a heat shield to protect it during its close pass of the sun, and relying on its smaller, less efficient antenna to beam its observations back to us.
While there’s little we can learn from NASA’s and ESA’s new images without the full complement of scientific data, it’s a good reminder that human space exploration pays off in unexpected ways. Hubble and Juice number among a dozen spacecraft that have observed 3I/ATLAS from around the solar system, including Mars rovers, solar orbiters, asteroid trackers and space telescopes that were never intended to track comets.
And there’s more to come: As 3I/ATLAS draws closer to Earth, the James Webb Space Telescope will take another look at it, while countless scientific observatories and amateur astronomers will have their chance to watch it as well. When you’re dealing with a mysterious intruder from parts unknown, every observation matters.